Pinch or prune back young plants regularly in the first year to encourage long-term development of a strong bushy structure. Don’t worry about sacrificing flowers the first year, you will be repaid with more flowers and a longer lived better looking plant for many years in the future. Young plants allowed to develop too many long flower stocks without this pinching back in the first couple years commonly break apart under the weight of their own flowers (S). After spring / early summer flowering, can be headed back by removing as much of the new-ish growth as desired (1). Doing so immediately after the first bloom encourages subsequent blooms, but sacrifices the development of seeds for wildlife to eat (S). Remove dead seed heads in the Fall (October), and prune as necessary (1). Consider leaving some of the pruned dry seed heads in the garden for food, nesting material, and habitat for birds and other critters you want around (S). Cut back by 1/3 to 1/2 or more of the leafy part of the branches in Fall to keep compact form, just make sure to leave at least two leafy nodes per branch as plants might not push new growth if cut below leafy nodes into old wood (3). References